Throughout this application various publications are referred to to provide background information useful for a complete understanding of the invention. The disclosures of these references are hereby incorporated in their entireties into the present application.
Immunoassays for human chorionic gonadotropin (hCG) are known and have been widely used, particularly in the diagnosis of pregnancy. Recent advances in immunology involving hybridomas and monoclonal antibodies have greatly increased the sensitivity of previous immunoassays. See, for example, Ehrlich, P.H. et al., Journal of Immunology 128:2709 (1982); Wada, H.G. et al., Clin. Chem., 28:1862 (1982); Shimizu, S.Y. et al., Clin. Chem., 28:546 (1982); and Pettersson, K. et al., Clin. Chem., 29:60 (1983). Serum-derived antibodies have also been employed. See, for example, Sekiya, T. et al., Acta Endocrinologica 97:562 (1981); Ayala, A.R. et al., J. Clinical Endocrinology and Medicine, 47:767 (1978) and Wehmann, R.E. et al., Amer. J. of Obstetrics and Gynecology, 140:753 (1981). Immunoassays involving serum-derived antibodies have included antibodies directed to the unique carboxy terminal portion of the .beta. subunit of hCG (ibid.; and Birken, S. et al., Endocrinology, 110:1555 [1982]).
Although previous improvements in hCG immunoassays have provided increased sensitivity or specificity, or both, it has not been possible until the present invention to obtain the greatly enhanced sensitivity and almost absolute specificity achieved using the immunoassay disclosed and claimed herein. This new immunoassay permits detection of smaller increases in hCG levels, and detection much sooner after insemination, than previously possible. It also permits hCG measurements in cancer diagnosis unimpaired by significant hLH cross-reactions.